1. Field of the Invention
The present invention relates to an exhausting method and a gas processing apparatus for introducing a flammable process gas into a chamber, performing a complete enclosure process, exhausting the process gas inside the chamber, and diluting the exhausted flammable gas for making the exhausted flammable gas purify.
2. Description of the Related Art
In manufacturing semiconductor devices, a semiconductor wafer is held in a chamber, and a flammable process gas is introduced into the chamber to a predetermined pressure in a state where an exhaust line is closed, and then a complete enclosure process is performed under the predetermined pressure.
For example, it has recently been suggested that a recovery process be performed by using a flammable silylating agent such as N-Trimethylsilyldimethylamine (hereinafter, referred to as TMSDMA) or the like in order to recover from damage applied to a low dielectric constant (hereinafter, referred to as low-K) film having a low parasitic capacitance during an etching process or a process removing a resist film (ashing) when the low-K film is used as an interlayer insulation film (Patent Reference 1). The recovery process is performed as the complete enclosure process described above.
After performing the complete enclosure process using the flammable gas, when the flammable gas inside the chamber is exhausted, as a safety policy, the exhausted flammable gas needs to be diluted to a lower explosive limit and additionally be purified by using a purification system.
However, if an exhaust valve is opened simply to a predetermined opening degree, a large amount of gas is exhausted in an initial stage. Thus, in a case of the flammable gas having a low level of the lower explosive limit, an enormous amount of diluting gas is necessary, and thus a process capability of the purification system is exceeded. In addition, a suitable amount of the diluting gas has to be supplied for the large amount of exhaust in the initial stage, and thus a large amount of the diluting gas is used wastefully. If the exhaust amount in the initial stage is set to be low to address the above problem, a throughput is degraded.
3. Prior Art Reference
(Patent Reference 1) Japanese Patent Laid-open Publication No. 2006-049798